Hallux valgus deformities in the human foot typically relate to at least one of two conditions: a deviated position of the great toe where the great toe leans in towards the second toe, and a deviation in the angle between the first and second metatarsal bones of the foot. The most commonly used medical terms associated with these deformities are “hallux valgus” and “hallux abducto valgus,” where “hallux” refers to the great toe, “valgus” refers to the abnormal slant of the great toe, and “abducto” refers to the abnormal slant or leaning of the great toe towards the second toe, as shown in FIGS. 1A and 1B.
There are generally four stages in the development of hallux abducto valgus (“HAV”). Stage one involves a lateral shift of the entire hallux upon the first metatarsal head. Stage two relates to abduction of the hallux. In stage three, because abduction of the hallux displaces the long flexor and extensor tendons laterally, contraction of these muscles during the propulsive period produces a retrograde medially directed component of force as the proximal phalanx pushes the first metatarsal in an adducted position. Finally, stage four involves complete dislocation of the first MPJ, which rarely occurs without underlying rheumatic inflammatory disease or neuromuscular disorder. In some situations, HAV may lead to the formation of a bunion. “Bunion” refers to the pathological bump, callous, and/or inflammation on the side of the great toe joint associated with either a bursal sac or a bone deformity.
The abnormalities associated with development of hallux valgus as described above are caused by a biomechanical abnormality, where certain tendons, ligaments, and supportive structures of the first metatarsal are no longer functioning correctly. While the underlying mechanisms are not fully understood, this biomechanical abnormality may be due to the structure of the foot (such as flat feet, excessive ligamentous flexibility, or abnormal bone structure), certain neurological conditions, poor-fitting footwear, or just chronic “wear and tear” leading to a progression of initially small irregularities.
Various treatments for hallux valgus and/or bunions exist. Various surgical procedures may address some combination of removing the abnormal bony enlargement of the first metatarsal, realigning the first metatarsal relative to the adjacent metatarsal, straightening the great toe relative to the first metatarsal and adjacent toes, realigning the cartilagenous surfaces of the great toe joint, repositioning the sesamoid bones beneath the first metatarsal, and correcting any abnormal bowing or misalignment within the great toe. Further treatments can include bunion pads and external splints. All of these known treatments have shortcomings in either effectiveness (pads and splints) or invasiveness (the surgical procedures). With respect to the existing surgical procedures, the vast majority require an osteotomy which leads to long recovery and the need for patients to wear a cast or surgical boot for weeks following the operation. Further, the surgical patients are left with a significant scar and poor cosmesis. In addition, studies have highlighted that as many as 30% of bunion surgery patients are unhappy with the result and nearly 10% have post-surgical complications. Finally, the surgical procedures are costly, requiring anesthesia, a lengthy operating time, and multiple trained medical staff.